Abstract: This study investigated the influence of sodium chloride solution (NaCl) on the physical properties of cement pastes incorporating fly ash as compared with plain cement pastes. The ordinary Portland cement was partially substituted with 35% fly ash (class F) by weight. The blended cement specimens were prepared using the standard water of consistency. Cement paste samples hydrated for 3, 14 and 28 days were immersed in NaCl solutions with different concentrations ranging from 0.5% up to 1.5%. The effect of NaCl attack on bulk density, porosity, chemically bound water, relative expansion and loss of weight was studied using the standard techniques. The results showed that, cement pastes incorporating fly ash are characterized by high resistance to chloride attack that plain cement, the porosity of fly ash B cement pastes are less than that of plain cement pastes.